Backlight unit and liquid crystal display including the same

ABSTRACT

A liquid crystal display includes a liquid crystal display panel, a backlight and a cover. The backlight includes optical sheets that are configured to be mounted to the cover using a plurality of holes provided on the optical sheet that material to corresponding protrusions provided on the cover. The holes and protrusions are configured to reduce damage or misalignment to the optical sheet that may be caused by heat generated inside the liquid crystal display.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This applicationNotice: More than one reissue application has been filedfor the reissue of U.S. Pat. No. 8,625,049. The reissue applications areapplication Ser. No. 14/536,540 filed on Nov. 7, 2014 (the presentapplication) and Ser. No. 14/967,790 filed on Dec. 14, 2015, which is acontinuation reissue of reissue application Ser. No. 14/536,540. U.S.Pat. No. 8,625,049 claims the benefit of Korean Patent Application No.10-2010-0022199 filed in Korea on Mar. 12, 2010 and U.S. ProvisionalApplication No. 61/306,514 filed on Feb. 21, 2010, which are herebyincorporated by reference.

BACKGROUND

1. Field

A backlight unit and a liquid crystal display including the same aredisclosed herein.

2. Background

Back light units and liquid crystal displays including the same areknown. However, they suffer from various disadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements, wherein:

FIG. 1 illustrates a liquid crystal display (LCD) according to anembodiment;

FIGS. 2 and 3 illustrate a backlight unit according to the embodiment;

FIGS. 4A to 4K illustrate an optical sheet according to the embodiment;

FIGS. 5A to 5C illustrate a housing and a fixing part according to theembodiment;

FIG. 6 illustrates shapes of a hole of the optical sheet and the fixingpart of the housing;

FIG. 7 illustrates a liquid crystal display panel and the optical sheetcoupled with the housing according to the embodiment;

FIGS.FIG. 8A and 8D areis an enlarged viewsview of a portion ‘C’ in FIG.7;

FIGS.FIG. 8B and 8E areis an enlarged viewsview of a portion ‘D’ in FIG.7;

FIGS.FIG. 8C and 8G areis an enlarged viewsview of a portion ‘E’ in FIG.7 and FIG. 8F is an enlarged view of a portion ‘F’ in FIG. 7;

FIG. 8D is an enlarged view of a portion ‘D’ in FIG. 7;

FIG. 8E is an enlarged view of a portion ‘E’ in FIG. 7;

FIG. 8F is an enlarged view of a portion ‘C’ in FIG. 7;

FIG. 8G is an enlarged view of a portion ‘F’ at a side of an opticalsheet in FIG. 7;

FIGS. 9A and 9B are sectional views of the LCD according to theembodiment;

FIGS. 10 and 11 illustrate a backlight unit and an optical assemblyaccording to another embodiment;

FIG. 12 illustrates a direct type backlight unit;

FIG. 13 illustrates an LCD according to another embodiment; and

FIG. 14 illustrates an edge type backlight unit.

DETAILED DESCRIPTION

FIG. 1 illustrates a liquid crystal display (LCD) according to a firstembodiment of the invention. As shown in FIG. 1, the LCD 100 may includea liquid crystal display panel 110, a backlight unit 120, cover 130,housing 135, a driving unit 140, and a back case 150.

The liquid crystal display panel 110, on which an image may bedisplayed, may include a first and second substrates 111 and 112attached to face a liquid crystal layer interposed therebetween. Aplurality of scan lines and a plurality of data lines may cross in amatrix form to define a plurality of pixels on the first substrate 111called a thin film transistor (TFT) array substrate. Each pixel mayinclude a TFT to turn the pixel on or off and a pixel electrode toelectrically connect the TFT. Red (R), green (G), and blue (B) colorfilters corresponding to the plurality of pixels and black matrixessurrounding the color filters and covering non-display elements such asthe scan lines, the data lines, and the TFTs may be formed on the secondsubstrate 112 called a color filter substrate.

In addition, a transparent common electrode covering the non-displayelements may also be provided on the second substrate 112. A printedcircuit board (PCB) may be connected to at least one side of the liquidcrystal display panel 110 by a connection member such as a flexiblecircuit board or a tape carrier package (TCP), and may be tightlyattached to a rear surface of the housing 135 during a modularizationprocess.

In the liquid crystal display panel 110, when TFTs selected by the scanlines are turned on according to ON/OFF signals of a gate drivingcircuit 113, a data voltage of a data driving circuit 114 may betransferred to a corresponding pixel electrode through the data lines.Accordingly, an alignment direction of liquid crystal molecules may bechanged by an electric field generated by the data voltage between thepixel electrode and the common electrode.

The LCD 100 according to an embodiment may include the backlight unit120 that may provide light to the liquid crystal display panel 110 froma rear surface of the liquid crystal display panel 110. The backlightunit 120 may include an optical assembly 123 and a plurality of opticalsheets 125 disposed on the optical assembly 123.

The liquid crystal display panel 110 and the backlight unit 120 may bemodularized through the cover 130 and the housing 135. The cover 130 maybe positioned on the front surface of the liquid crystal display panel110, and may be a top cover shaped as a rectangular frame that may coveran upper surface and a side surface of the liquid crystal display panel110. A front surface of the cover 130 may be open to allow displaying ofan image generated on the liquid crystal display panel 110.

The housing 135 may be positioned on a rear surface of the backlightunit 120 and may include a bottom plate 135a and a supporting plate135b. The bottom plate 135a may be a bottom cover, to which the liquidcrystal display panel 110 and the backlight unit 120 are coupled, thatmay serve as a base for the LCD 100. The bottom plate 135a may be shapedas a single rectangular plate. The supporting plate 135b may support andcouple the cover 130 and the bottom plate 135a.

The driving unit 140 may be disposed on one surface of the housing 135positioned on the rear surface of the backlight unit 120. The drivingunit 140 may include a driving controller 141, a main board 142, and apower supply unit 143. The driving controller 141 may be a timingcontroller that adjusts an operation timing of each driving circuit ofthe liquid crystal display panel 110. The main board 142 may transfer avertical synchronous signal, a horizontal synchronous signal, and R, G,and B resolution signals to the timing controller. The power supply unit143 may provide power to the liquid crystal display panel 110 and thebacklight unit 120. The driving unit 140 may be coupled to the housing135 by using a driving unit chassis 145. The driving unit 140 may becovered by the back case 150.

FIGS. 2 and 3 illustrate a backlight unit according to the firstembodiment. Referring to FIGS. 2 and 3, the backlight unit 200 mayinclude an optical assembly 210 and an optical sheet 250. The opticalassembly 210 may include a first layer 215, a plurality of light sources217, a reflective layer 220, a second layer 230, and a diffusion plate240. The plurality of light sources 217 may be formed on the first layer215, and the second layer 230 may be disposed on the first layer 215 tocover the plurality of light sources 217.

The first layer 215 may be a board (or substrate) on which the pluralityof light sources 217 may be mounted. An electrode pattern may be formedon the first layer 215 in order to connect an adapter that may supplypower and the light sources 217. For example, a carbon nano-tube (CNT)electrode pattern for connecting the light sources 217 and the adaptermay be formed on an upper surface of the substrate. The first layer 215may be a PCB formed of polyethylene terephthalate (PET), glass,polycarbonate (PC), silicon (Si), or other appropriate materials onwhich the plurality of light sources 217 may be mounted. The first layer215 may also be formed as a film.

The light sources 217 may be one of a light emitting diode (LED) chipand an LED package including at least one LED chip. In this embodiment,simply for ease of explanation, light sources 217 will be describedherein as having an LED package.

The LED package constituting the light sources 217 may be classifiedinto a top view type LED package and a side view type LED packagedepending on the direction of a light emission surface. The lightsources 217 may be configured by using at least one of a top view typeLED package in which a light emission surface may be formed toward theupper side and a side view type LED package in which the light emissionsurface may be formed toward the side. When the light sources 217 arethe side view type LED package, the light emission surface of each ofthe plurality of light sources 217 may be disposed on the side, and theplurality of light sources 217 may emit light in a lateral direction,for example, in the direction in which the first layer 215 or thereflective layer 220 extends. Thus, the thickness of the second layer230 formed on the light sources 217 may be reduced, making the backlightunit 200 and the LCD 100 thinner.

The light sources 217 may be color LEDs that may emit at least one ofred, blue, and green colors, or white LEDs. The colored LEDs may includeat least one of red LEDs, blue LEDs, and green LEDs. Accordingly, thedisposition and color of light emitted from the LEDs may be variablymodified.

The second layer 230 may be disposed on the first layer 215 and maycover the plurality of light sources 217. The second layer 230 may allowlight emitted from the light sources 217 to transmit therethrough andspread the light, whereby the light emitted from the light sources 217may be uniformly provided to the liquid crystal display panel.

The reflective layer 220 may reflect light emitted from the lightsources 217 and may be positioned on the first layer 215. The reflectivelayer 220 may be formed on an area of the first layer 215, other thanthe area where the light sources 217 are formed. For example, as shownin FIG. 3, reflective layer 220 may include recesses corresponding tothe light sources 217 in which the light sources 217 may be positioned.The reflective layer 220 may reflect light emitted from the lightsources 217 and reflect again light totally reflected from the boundaryof the second layer 230 to further increase the area of lightdispersion.

The reflective layer 220 may contain at least one of metal or a metaloxide, a reflective material. For example, the reflective layer 220 maybe formed of metal or metal oxide having a high reflectance, forexample, aluminum (Al), silver (Ag), gold (Au), titanium dioxide (TiO2),or other appropriate reflective materials. The reflective layer 220 maybe formed by depositing or coating the metal or metal oxide on the firstlayer 215 or by printing metal ink on the first layer 215. Here, avacuum deposition method, for example, a thermal deposition method, anevaporation method, a sputtering method, or other appropriate depositionmethods may be used as the deposition method. Further, a printingmethod, a gravure coating method, a silk screen method, or otherappropriate methods may be used as the coating or printing method.

The second layer 230 on the first layer 215 may be formed of alight-transmissive material, for example, a silicon or acrylic resin.However, the second layer 230 is not limited thereto and may be formedof various other resins. In order to allow the backlight unit 200 tohave a uniform luminance in diffusing light emitted from the lightsources 217, the second layer 230 may be formed of a resin having arefractive index of about 1.4 to 1.6. For example, the second layer 230may be formed of polyethylene terephthalate (PET), polycarbonate (Pr),polypropylene (PP), polyethylene (PE), polystyrene (PS), polyepoxy (PE),silicon, acryl, or other appropriate materials.

The second layer 230 may include a polymer resin having an adhesiveproperty so as to be firmly and tightly attached to the light sources217 and the reflective layer 220. For example, the second layer 230 maybe formed of acryl group, urethane group, epoxy group, and melaminegroup such as unsaturated polyester, methyl methacrylate, ethylmethacrylate, isobutyl methacrylate, n-butyl methacrylate, n-butylmethyl methacrylate, acrylic acid, methacrylic acid, hydroxyl ethylmethacrylate, hydroxyl propyl methacrylate, hydroxyl ethyl acrylate,acrylamide, methylol acrylamide, glycidyl methacrylate, ethyl acrylate,isobutyl acrylate, n-butyl acrylate, 2-ethyl hexyl acrylate polymer,copolymer, terpolymer, other appropriate materials.

The second layer 230 may be formed by coating a liquid or gel phaseresin on the first layer 215 having the plurality of light sources 217and the reflective layer 220 formed thereon, and then hardening theresin. Alternatively, the second layer 230 may be formed by coating aresin on a support sheet, partially hardening the resin, and thenbonding the same to the first layer 215.

The diffusion plate 240 may be formed on the second layer 230 that mayallow light emitted from the light sources 217 to be diffused upward.The diffusion plate 240 may be bonded to the second layer 230 using anadditional adhesive member.

FIGS. 4A to 4K illustrate an optical sheet according to the firstembodiment. The optical sheet 250 may be positioned on the foregoingoptical assembly 210. Referring to FIG. 4A, the optical sheet 250according to this embodiment may be a diffusion sheet that may diffuselight outputted from the light sources or a prism sheet that mayconcentrate light.

The optical sheet 250 may include a plurality of holes or slots 251 onat least one side such that the optical sheet 250 may be coupled to thecover 130 or the housing 135. The plurality of holes 251 may be shapedas a slot. Hence, in the present application, holes 251 may also bereferred to as slots 251. The optical sheet 250 may have a rectangularshape, and the plurality of holes 251 may be positioned on the upperside 255 and lower side 256 of the optical sheet 250. Here, the upperside 255 of the optical sheet 250 may correspond to an upper side of theLCD when assembled and positioned to stand or mounted for use. Likewise,the lower side 256 of the optical sheet 250 may correspond to a lowerside of the LCD.

The holes 251 may be formed at protrusions or tabs 252 protruded from atleast one side of the optical sheet 250, for example, at the upper side255 and the lower side 256 of the optical sheet 250. The protrusions 252may subsequently be coupled with the cover 130 or the housing 135, andmay be formed such that they protrude from one side of the optical sheet250.

The holes 251 formed at the protrusions 252 may have various shapesincluding a polygonal shape, a triangular shape, a circular shape, aquadrangular shape, or other appropriate shapes. Also, the protrusions252 may have various shapes that allow the protrusions 252 to be easilycoupled with the cover 130 or the housing 135. For example, the portionsof the protrusions 252 in contact with the cover 130 or the housing 135may have a large quadrangular shape.

The plurality of holes 251 may be formed such that a number of holes 251formed on one of the plurality of sides of the optical sheet 250 is lessthan a number of holes 251 formed on another of the plurality of sidesof the optical sheet 250. For example, as shown in FIG. 4A, the numberof holes 251 formed on the upper side 255 of the optical sheet 250 maybe greater than the number of holes 251 formed on the lower side 256 ofthe optical sheet 250. As discussed above, the upper side 255 of theoptical sheet 250 may correspond to the upper side of the LCD when theLCD is assembled. In order to prevent the optical sheet 250 from saggingdue to the weight of the LCD components when assembled, a greater numberof holes 251 may be formed on the upper side 255.

A plurality of holes 251 may also be formed on the sides of the opticalsheet 250 which face each other. For example, as shown in FIGS. 4A to4F, the plurality of holes 251 may be positioned on the upper side 255and the lower side 256 of the optical sheet 250 which face each other.The plurality of holes 251 may also be positioned on the left side 257and the right side 258 of the optical sheet 250. Moreover, the pluralityof holes 251 may be positioned on all sides, for example, on the upperside 255, the lower side 256, the left side 257, and the right side 258.

Referring to FIG. 4B, the plurality of holes 251 formed on the upperside 255 of the optical sheet 250 may be positioned to be symmetricalwith the plurality of holes 251 formed on the lower side 256 of theoptical sheet which faces the upper side 255. Alternatively, withreference to FIG. 4A, the plurality of holes 251 formed on the upperside 255 of the optical sheet 250 may be asymmetrical with the pluralityof holes 251 formed on the lower side 256 of the optical sheet 250 whichfaces the holes 251 of the upper side 255.

Referring to FIGS. 4C and 4D, the plurality of holes 251 may bepositioned on all of the sides, for example, on the upper side 255, onthe lower side 256, on the left side 257, and on the right side 258 ofthe optical sheet 250. Here, as shown in FIG. 4C, the plurality of holes251 disposed on the upper side 255 of the optical sheet 250 may besymmetrical to the plurality of holes 251 disposed on the lower side 256of the optical sheet 250, and the plurality of holes 251 disposed on theleft side 257 of the optical sheet 250 may be symmetrical to theplurality of holes 251 disposed on the right side 258 of the opticalsheet 250. Alternatively, as shown in FIG. 4D, the plurality of holes251 disposed on the upper side 255 of the optical sheet 250 may beasymmetrical to the plurality of holes 251 disposed on the lower side256 of the optical sheet 250, and the plurality of holes 251 disposed onthe left side 257 of the optical sheet 250 may be asymmetrical to theplurality of holes 251 disposed on the right side 258 of the opticalsheet 250.

Referring to FIGS. 4E to 4F, the plurality of holes 251 may bepositioned on the sides of the optical sheet 250, for example, on theleft side 257 and right side 258 which face each other. Here, theplurality of holes 251 are not positioned on the upper and lower sides255 and 256 of the optical sheet 250. As shown in FIG. 4E, the pluralityof holes 251 disposed on the left side 257 of the optical sheet 250 maybe symmetrical to the plurality of holes 251 disposed on the right side258 of the optical sheet 250. Alternatively, as shown in FIG. 4F, theplurality of holes 251 disposed on the left side 257 of the opticalsheet 250 may be asymmetrical to the plurality of holes 251 disposed onthe right side 258 of the optical sheet 250.

Referring now to FIG. 4G, the holes or slots 251 may be formed at aninner side of at least one side of the optical sheet 250, for example,at an inner side of the upper side 255 and the lower side 256 of theoptical sheet 250. For example, the slots or holes 251 may be formed onthe optical sheet 250 inside the side edges thereof. The plurality ofholes 251 formed at an inner side of at least one side of the opticalsheet 250 may be formed on the sides of the optical sheet 250 which faceeach other. For example, as shown in FIGS. 4G and 4I, the plurality ofholes 251 may be positioned at the inner side of the upper side 255 andthe lower side 256 of the optical sheet 250 which face each other.Further, the plurality of holes 251 may be positioned at the inner sideof the left and right sides 257 and 258 of the optical sheet 250, andthe plurality of holes 251 may be positioned at the inner side of theupper, lower, left, and right sides 255, 256, 257, and 258,respectively, of the optical sheet 250.

Further, with reference to FIG. 4G, the plurality of holes 251 formed atthe inner side of the upper side 255 of the optical sheet 250 may beasymmetrical to the plurality of holes 251 formed at the inner side ofthe lower side 256 of the optical sheet 250 which faces the upper side255. Also, with reference to FIG. 4I, the plurality of holes 251 formedat the inner side of the left side 257 of the optical sheet 250 may besymmetrical to the plurality of holes 251 formed at the inner side ofthe right side 256 of the optical sheet 250 which faces the left side255.

As shown in FIG. 4H, the plurality of holes 251 may be positioned at theinner side of all of the sides, for example, at the inner side of theupper, lower, left, and right sides 255, 256, 257, and 258 of theoptical sheet 250. Also, as shown in FIG. 4I, the plurality of holes 251may be positioned at the inner side of the sides, for example, at theinner side of the left and right sides 257 and 258 of the optical sheet250 that face each other. Here, the plurality of holes 251 are notpositioned at the upper and lower sides 255 and 256 of the optical sheet250.

Referring now to FIG. 4J, the plurality of holes 251 may be positionedat the four corners 259 of the optical sheet 250. Alternatively, asshown in FIG. 4K, the plurality of holes 251 may be positioned atopposite corners 259 of the optical sheet 250 that face each other.

As described above, the optical sheet 250 according to the firstembodiment may include the plurality of holes 251 on at least one sideor at the corners thereof to fixedly couple the optical sheet 250 to thecover 130 or the housing 135. Thus, the reliability of the coupledoptical sheet 250 and cover 130 or the housing 135 may be improved.Further, the optical characteristics of light emitted from the lightsources may be effectively enhanced. The disposition of the holes of theoptical sheet as illustrated in FIGS. 4A to 4K are not limited to thisembodiment, and may be disposed, for example, only at one side of theoptical sheet to couple with the cover or the housing.

FIGS. 5A to 5C illustrate a cover and a fixing part according to thisembodiment. Referring now to FIG. 5A, a cover 300 may have a shape of arectangular frame and, as shown in FIG. 1, the cover 300 may cover thefront side of the LCD 100. A fixing part 310 to couple the optical sheet250 may be formed as a rail and may be positioned on a side wall of thecover 300. For example, a plurality of fixing parts 310 may be providedand positioned on at least one side wall of the cover 300. Further, asshown in FIG. 5A, the fixing parts 310 may be positioned on upper andlower side walls 321 and 322. The fixing parts 310 may be alsopositioned on left and right side walls 323 and 324 of the cover 300.The placement of the fixing parts 310 may correspond to the placement ofthe holes 251 of the optical sheet 250 as described above.

The fixing parts 310 may be formed on a step portion 315 of the sidewalls 323 and 324 of the cover 300 such that it may protrude upward fromthe side walls 323 and 324. The protrusion may have a hexahedral shape,cylindrical shape, spherical shape, or other appropriate shape and isnot particularly limited thereto. Further, as described above the fixingpart may also be formed as a rail. Hence, the fixing part 310 may alsobe referred to herein as a rail 310. The step portion 315 may be a sizesufficient to allow a hole 251 formed at a protrusion 252 of the opticalsheet 250 to be mounted thereon. Further, the fixing part 310 may bepositioned at a central portion of the step portion 315. The size of thefixing part 310 formed at the step portion 315 may be the same as thatof the hole 251 formed on the protrusion 252, or may be slightly largerthan that of the hole 251. Accordingly, the hole 251 of the opticalsheet 250 may be coupled with the fixing part 310 of the cover 300 tofix the optical sheet 250 to the cover 300.

Referring to FIG. 5B, the step portions 315 may be formed along anentire lateral length of the side wall of the cover 300. The stepportions 315 may be formed on the entire upper side wall 321 of thecover 300, and the step portions 315 may be formed on the entire lowerside wall 322 of the cover 300.

The fixing parts 310 may be disposed on the step portions 315. The stepportions 315 illustrated in FIG. 5B may allow mounting of the opticalsheet illustrated in FIGS. 4G and 4I having the plurality of holesformed at the inner side of one side thereof. In this case, theplurality of holes formed on the optical sheets may be coupled to thefixing parts 310 formed at the step portions 315 of the cover 300.

As shown in FIG. 5C, the fixing parts 310 may be positioned at thecorners 325 of the cover 300. Here, the fixing parts 310 may be disposedto be slanted, or diagonally, at the corners 325, but is not limitedthereto. Thus, the optical sheet illustrated in FIGS. 4J and 4K asdescribed above, for example, the optical sheet having the plurality ofholes at the corners may be coupled to the fixing parts 310 positionedat the corners 325 of the cover 300.

FIG. 6 illustrates the shapes of the hole of the optical sheet and thefixing part of the cover. The holes 251 of the optical sheet 250 and thefixing parts 310 of the cover 300 may have a quadrangular shape or anyother appropriate shapes. The hole 251 of the optical sheet 250 or thefixing part 310 of the cover 300 may have a rectangular shape as shownin FIG. 6(a). Also, the hole 251 of the optical sheet 250 or the fixingpart 310 of the cover 300 may have a square shape as shown in FIG. 6(b)or a pentagonal shape as shown in FIG. 6(c). However, the shapes are notlimited thereto and the hole 251 of the optical sheet 250 or the fixingpart 310 of the cover 300 may have any appropriate shapes including apolygonal shape having more sides than the pentagonal shape.

Also, the hole 251 of the optical sheet 250 or the fixing part 310 ofthe cover 300 may have a circular shape as shown in FIG. 6(d) or an ovalshape as shown in FIG. 6(e). The shapes of the hole 251 of the opticalsheet 250 or the fixing part 310 of the cover 300 are not limitedthereto, and they may have any shape so long as it may allow for thecoupling of the hole 251 of the optical sheet 250 and the fixing part310 of the cover 300.

Hereinafter, the configuration in which the hole 251 of the opticalsheet 250 and the fixing part 310 of the cover 300 are coupled will nowbe described in detail. Simply for ease of explanation, the hole 251 ofthe optical sheet 250 and the fixing part 310 of the cover 300 will bedescribed with reference to a hole having a rectangular shape.

FIG. 7 illustrates the liquid crystal display panel and the opticalsheet coupled to the cover according to an embodiment; FIG. 8A and 8Dare is an enlarged view of a portion ‘C’ in FIG. 7; FIG. 8B and 8D areis an enlarged view of a portion ‘D’ in FIG. 7; and FIG. 8C and 8F areis an enlarged view of a portion ‘E’ in FIG. 7; and FIG. 8G is anenlarged view of a portion ‘F’ in FIG. 7 FIG. 8D is an enlarged view ofa portion ‘D’ in FIG. 7; FIG. 8E is an enlarged view of a portion ‘E’ inFIG. 7; FIG. 8F is an enlarged view of a portion ‘C’ in FIG. 7; FIG. 8Gis an enlarged view of a side of an optical sheet in FIG. 7; and FIG. 8Fis an enlarged view of portion ‘F’ in FIG. 7.

As shown in FIG. 7, a liquid crystal display panel 400 may be positionedon the cover 300, and the optical sheet 250 may be positioned on theliquid crystal display panel 400. A plurality of gate driving circuits410 may be disposed at left and right sides of the liquid crystaldisplay panel 400, and a printed circuit board (PCB) 420 may be disposedon the optical sheet 250 on the liquid crystal display panel 400. Aplurality of data driving circuits 430 may be disposed on the PCB 420.

Here, the optical sheet 250 may be disposed on the cover 300 such thatthe holes 251 of the optical sheet 250 may be coupled with the fixingparts 310 of the cover 300. For example, referring to enlarged portion‘A’ in FIG. 7, the slot or hole 251 that may be formed at the tab orprotrusion 252 and disposed at the upper side of the optical sheet 310may be coupled with the rail or fixing part 310 formed at the upper sidewall of the cover 300. For example, the fixing part 310 may be insertedinto the hole 251 of the optical sheet 250.

Referring to a portion ‘B’ in FIG. 7, the hole 251 that may be formed atthe protrusion 252 and disposed at the lower side of the optical sheet310 may be coupled with the fixing part 310 formed at the lower sidewall of the cover 300. Here, the protrusions 252 of the optical sheet250 and the fixing parts 310 of the cover 300 may be disposed betweenthe data driving circuits 430 of the liquid crystal display panel 400.

For example, in order to secure an area at the side of the cover 300where the data driving circuits 430 may be mounted, the fixing parts 310may be disposed between the data driving circuits 430, and theprotrusions 252 and the holes 251 of the optical sheet 250 may bedisposed between the data driving circuits 430 according to thedisposition of the fixing parts 310.

Referring to FIG. 8A, enlarged portion ‘C’ shows the hole 251 that maybe coupled to the fixing part 310 at the edge on the upper side of theoptical sheet 250. Here, the hole 251 may include a first side 251a, asecond side 251b, a third side 251c, and a fourth side 251d, and thefixing part 310 may include a fifth side 310a facing the first side 251aof the hole 251, a sixth side 310b facing the second side 251b, aseventh side 310c facing the third side 251c, and an eighth side 310dfacing the fourth side 251d. Here, the first side 251a of the hole 251may be adjacent to the cover 300, and the second side 251b may beseparated to be positioned away from the cover 300.

For example, in the enlarged portion ‘C’ where the hole 251 may becoupled to the fixing part 310 at the edge on the upper side of theoptical sheet 250, a first distance d1 may be formed between the firstside 251a of the hole 251 and the fifth side 310a of the fixing part310, a second distance d2 may be formed between the second side 251b ofthe hole 251 and the sixth side 310b of the fixing part 310, a thirddistance d3 may be formed between the third side 251c of the hole 251and the seventh side 310c of the fixing part 310, and a fourth distanced4 may be formed between the fourth side 251d of the hole 251 and theeighth side 310d of the fixing part 310.

The first distance d1 may range from 0.05 mm to 0.3 mm, and maypreferably be 0.1 mm. Here, when the first distance d1 is longer than0.05 mm, a sufficient margin may be provided to allow for an expansionof the optical sheet 250 due to heat generated in the LCD. Thus, acrease in the optical sheet 250 due to thermal expansion mayadvantageously be prevented. When the first distance d1 is shorter than0.3 mm, tension may be caused on the optical sheet 250 by the fixingpart 310 when the optical sheet 250 contracts as heat dissipates fromthe optical sheet 250. Thus, a crease in the optical sheet 250 due tothermal contraction may advantageously be prevented.

The second distance d2 may range from 0.1 mm to 1 mm, and may preferablybe 0.5 mm. Here, when the second distance d2 is longer than 0.1 mm, asufficient margin may be provided to allow for an expansion of theoptical sheet 250 due to heat generated in the LCD. Thus, a crease inthe optical sheet 250 due to thermal expansion may advantageously beprevented. When the second distance d2 is shorter than 1 mm, the seconddistance d2 between the fixing part 310 and the hole 251 may increase asthe optical sheet 250 contracts as heat dissipates from the opticalsheet 250, thus advantageously preventing the hole 251 from beingreleased from the fixing part 310. For example, a length of the slot orhole 251 may be 0.15 mm to 1.3 mm larger than a length of the rail orfixing part 310.

The third distance d3 and the fourth distance d4 may range from 1 mm to5 mm, and may preferably be 2 mm. Here, when the third distance d3 andthe fourth distance d4 are longer than 1 mm, a sufficient margin may beprovided to allow for an expansion of the optical sheet 250 due to heatgenerated in the LCD, thus a crease in the optical sheet 250 mayadvantageously be prevented. When the third distance d3 and the fourthdistance d4 are shorter than 5 mm, the third distance d3 and the fourthdistance d4 between the fixing part 310 and the hole 251 may increase,thus advantageously preventing the hole 251 and the fixing part 310 frombeing released. For example, a width of the slot or hole 251 may be 2 mmto 10 mm larger than a width of the rail or fixing part 310.

Referring to FIG. 8B, enlarged portion ‘D’ shows the hole 251 that maybe coupled to fixing part 310 at the center among the holes 251 disposedon the upper side of the optical sheet 250. Here, a fifth distance d5may be formed between the first side 251a of the hole 251 and the fifthside 310a of the fixing part 310, a sixth distance d6 may be formedbetween the second side 251b of the hole 251 and the sixth side 310b ofthe fixing part 310, a seventh distance d7 may be formed between thethird side 251c of the hole 251 and the seventh side 310c of the fixingpart 310, and an eighth distance d8 may be formed between the fourthside 251d of the hole 251 and the eighth side 310d of the fixing part310.

The fifth distance d5 may range from 0.05 mm to 0.3 mm, and maypreferably be 0.1 mm. Here, when the fifth distance d5 is longer than0.05 mm, a sufficient margin may be provided to allow for an expansionof the optical sheet 250 due to heat generated in the LCD. Thus, ceasingof the optical sheet 250 may be prevented. When the fifth distance d5 isshorter than 0.3 mm, tension may be created on the optical sheet 250 bythe fixing part 310 as the optical sheet 250 contracts due todissipation of heat, thus advantageously preventing the optical sheet250 from being creased.

The sixth distance d6 may range from 0.1 mm to 1 mm, and may preferablybe 0.5 mm. Here, when the sixth distance d6 is longer than 0.1 mm, amargin sufficient for thermal expansion of the optical sheet 250 may beprovided, thus advantageously preventing the optical sheet 250 frombeing creased. When the sixth distance d6 is shorter than 1 mm, thesixth distance d6 between the fixing part 310 and the hole 251 mayincrease as the optical sheet 250 contracts as heat is dissipated, thusadvantageously preventing the hole 251 from being released from thefixing part 310. For example, the length of hole 251 may be 0.15 mm to1.3 mm larger than a length of the rail or fixing part 310.

The seventh distance d7 and the eighth distance d8 may range from 0.1 mmto 1 mm, and may preferably be 0.5 mm. Here, when the seventh distanced7 and the eighth distance d8 are longer than 0.1 mm, a sufficientmargin may be provided to allow for an expansion of the optical sheet250 due to heat generated in the LCD, thus a crease in the optical sheet250 may advantageously be prevented. When the seventh distance d7 andthe eighth distance d8 are shorter than 1 mm, the hole 251 and thefixing part 310 may serve to fix the optical sheet 250 at the centralportion of the optical sheet 250, thus advantageously preventing theoptical sheet 250 from being distorted at its position. For example, awidth of the slot or hole 251 may be 0.15 mm to 1.3 mm larger than awidth of the rail or fixing part 310.

As discussed above with reference to FIGS. 8A and 8B, the seventhdistance d7 and the eighth distance d8 between the hole 251 and thefixing part 310 disposed at enlarged portion ‘D’ positioned near acentral portion of optical sheet 250 may be shorter than the thirddistance d3 and the fourth distance d4 between the hole 251 and thefixing part 310 disposed at enlarged portion ‘C’.

As for the relationship between the hole 251 and the fixing part 310disposed at the central portion ‘D’ of the optical sheet 250, they maybe positioned near a central portion of the optical sheet 250 and mayserve to fix the overall position of the optical sheet 250 as statedabove. Accordingly, the optical sheet 250 may be fixed to prevent itsposition from changing due to an expansion or contraction of the opticalsheet 250.

Also, as for the relationship between the hole 251 and the fixing part310 disposed at enlarged portion ‘C’ of the optical sheet 250, they maybe positioned at the edge of the optical sheet 250 to secure a marginsufficient to allow for the extraction and contraction of the opticalsheet 250. Thus, the third distance d3 and the fourth distance d4 may belarger than the corresponding distances at the central position ‘D’.

Referring to FIG. 8C, an enlarged portion ‘E’ shows the hole 251 thatmay be disposed at the lower side of the optical sheet 250 coupled tothe fixing part 310. Here, a ninth distance d9 may be formed between thefirst side 251a of the hole 251 and the fifth side 310a of the fixingpart 310, a tenth distance d10 may be formed between the second side251b of the hole 251 and the sixth side 310b of the fixing part 310, aneleventh distance d11 may be formed between the third side 251c of thehole 251 and the seventh side 310c of the fixing part 310, and a twelfthdistance d12 may be formed between the fourth side 251d of the hole 251and the eighth side 310d of the fixing part 310.

The ninth distance d9 may range from 0.1 mm to 1 mm, and may preferablybe 0.5 mm. Here, when the ninth distance d9 is longer than 0.1 mm, amargin sufficient to allow for thermal expansion of the optical sheet250 may be provided, thus advantageously preventing the optical sheet250 from being creased. When the ninth distance d9 is shorter than 1 mm,tension may be provided to the optical sheet 250 by the fixing part 310when the optical sheet 250 contracts as heat dissipates from the opticalsheet 250, thus advantageously preventing the optical sheet 250 frombeing creased.

The tenth distance d10 may range from 0.1 mm to 1 mm, and may preferablybe 0.5 mm. Here, when the tenth distance d10 is longer than 0.1 mm, amargin sufficient to allow for thermal expansion of the optical sheet250 may be provided, thus advantageously preventing the optical sheet250 from being creased. When the tenth distance d10 is shorter than 1mm, the tenth distance d10 between the fixing part 310 and the hole 251may increase as the optical sheet 250 contracts as heat dissipates fromthe optical sheet 250, thus advantageously preventing the hole 251 frombeing released from the fixing part 310. For example, a length of slotor hole 251 may be 0.2 mm to 2 mm larger than a length of rail or fixingpart 310.

The eleventh distance d11 and the twelfth distance d12 may range from 1mm to 5 mm, and may preferably be 2 mm. Here, when the eleventh distanced11 and the twelfth distance d12 are longer than 1 mm, a marginsufficient to allow for thermal expansion of the optical sheet 250 maybe provided, thus advantageously preventing the optical sheet 250 frombeing creased. When the eleventh distance d11 and the twelfth distanced12 are shorter than 5 mm, the eleventh distance d11 and the twelfthdistance d12 between the fixing part 310 and the hole 251 may belengthened, thus advantageously preventing the hole 251 and the fixingpart 310 from being released. For example, a width of slot or hole 251may be 2 mm to 5 mm larger than a width of rail or fixing part 310.

Moreover, the range of distances for d1 and d5 as described above areapplicable when the LCD 100 is positioned horizontally. However, whenthe LCD is positioned vertically, for example, when mounted on a standor on a wall for use, as enlarged portions ‘C’ and ‘D’ are positioned atthe upper side 255 of the optical sheet 250, distances d1 and d5 willbecome zero. Further, in the vertical position, distances d2, d6, d10,and d9 will adjust accordingly.

Meanwhile, with reference to FIG. 7, the one or more holes 251 of theoptical sheet 250 may be formed to correspond to the periphery of anactive area of the display panel 400. The active area of the displaypanel 400 may be an area on which an image is displayed, and theperiphery of the active area of the display panel 400 may be an areabetween an outer edge of the active area of the display panel 400 andthe cover 300. Here, the area between the outer edge of the active areaand the cover 300 may refer to an area extending from the outer edge ofthe active area to the cover 300. For example, the area may include thecover 300. The holes 251 of the optical sheet 250 may be positionedbetween the display panel 400 and the cover 300, and may be fixedlycoupled with the fixing parts 310 of the cover 300.

The holes 215 provided on the optical sheet 250 according to thisembodiment may be positioned on the upper side 255 and the lower side256 of the optical sheet 250, and the size of the holes 251 positionedon the upper side 255 of the optical sheet 250 may be different fromthat of the holes 251 positioned on the lower side 256 of the opticalsheet 250. For example, the size of the holes 251 positioned on theupper side 255 of the optical sheet 250 may be smaller than the size ofthe holes 251 positioned on the lower side 256 of the optical sheet 250.

FIG. 8D illustrates the hole 251 of the optical sheet 250 at a portion‘D’ in FIG. 7, FIG. 8E illustrates the hole 251 of the optical sheet 250at a portion ‘E’ in FIG. 7, and FIG. 8F illustrates the hole 251 of theoptical sheet 250 at a portion ‘C’ in FIG. 7. With reference to FIGS. 8Dand 8E, the length of a longer axis l1 and a shorter axis l2 of the hole251 positioned on the upper side 255 of the optical sheet 250illustrated in FIG. 8D may be shorter than the length of a longer axisl3 and a shorter axis l4 positioned on the lower side 256 of the opticalsheet 250 illustrated in FIG. 8E. Here, the longer axis of the hole 251may be the longest axis in an x-axis direction of the hole 251, and theshorter axis of the hole 251 may be the shortest axis in a y-axisdirection of the hole 251.

For example, the size of the hole 251 positioned on the upper side 255of the optical sheet 250 may be smaller than the size of the hole 251positioned on the lower side 256 of the optical sheet 250. Thus, asaforementioned, the hole 251 positioned on the upper side 255 of theoptical sheet 250 may act as a reference point for fixing the opticalsheet 250 to the cover 300 to prevent the optical sheet 250 from beingdeformed, for example, by heat, which may cause it to shift or move fromits original position. Further, the hole 251 positioned on the lowerside 256 of the optical sheet 250 may serve to provide a margin forthermal expansion when the optical sheet 250 is deformed by heat.

With reference to FIGS. 8D and 8F, the length of the longer axis l1 ofthe hole 251 positioned at a central portion of the upper side 255 ofthe optical sheet 250 illustrated in FIG. 8D may be shorter than thelength of the longer axis l5 of the hole 251 positioned at the edge ofthe upper side 255 of the upper side 255 of the optical sheet 250illustrated in FIG. 8F. Also, the length of the shorter axis l2 of thehole 251 positioned at the central portion of the upper side 255 of theoptical sheet 250 may be equal to the length of the shorter axis l6 ofthe hole 251 positioned at the edge of the upper side 255 of the opticalsheet 250.

For example, the size of the hole 251 positioned at the central portionof the upper side 255 of the optical sheet 250 may be smaller than thatof the hole 251 positioned at the edge of the upper side 255 of theoptical sheet 250. Thus, as previously discussed, the hole 251positioned at the central portion of the upper side 255 of the opticalsheet 250 may act as a reference point for fixing the optical sheet 250to the cover 300 to prevent the optical sheet 250 from being deformed,shifted, or moved due to thermal expansion, while the hole 251positioned at the edge of the upper side 255 of the optical sheet 250may serve to provide a margin for thermal expansion when the opticalsheet 250 is deformed by heat.

In the foregoing description, simply for ease of explanation, the fixingparts 310 have been described as being provided on the cover 300 andshaped as a rail. However, the present invention is not limited thereto.For example, the fixing parts 310 may be provided on the bottom plate ofthe housing and may be formed in any appropriate shape as previouslydescribed.

FIGS. 9A and 9B are sectional views of the LCD according to the firstembodiment. Specifically, FIG. 9A is a vertical sectional view of theupper side of the cover perpendicular to a lengthwise direction, andFIG. 9B is a vertical sectional view of the lateral side of the coverperpendicular to the lengthwise direction. As shown in FIGS. 9A and 9B,the LCD 100 may be configured such that a liquid crystal display panel400 is disposed on a front cover 300 and the optical sheet 250 isdisposed on the liquid crystal display panel 400. The optical sheet 250may be fixedly coupled with the cover 300. For example, the opticalsheet 250 may be fixedly coupled with the cover 300 such that the hole251 of the optical sheet 250 may be coupled with the fixing part 310provided at the side wall of the cover 300.

The optical assembly 210 may disposed on the optical sheet 250, and thecover 300 and a bottom plate 320 may be coupled by means of a screw 330.Here, as shown in FIG. 9A, at the upper side of the cover 300, a sideportion of the bottom plate 320 may be inserted into a side portion ofthe cover 300. Meanwhile, as shown in FIG. 9B, at the lateral side ofthe cover 300, the bottom plate 320 may be mounted on the cover 300 andcoupled by means of a screw 330.

As described above, in the LCD 100, the liquid crystal display panel400, the optical sheet 250, and the optical assembly 210 may be receivedin the cover 300 and the bottom plate 320, and the hole 251 of theoptical sheet 250 may be fixedly coupled to the fixing part 310 of thecover 300. Thus, the optical sheet 250 may be prevented from beingdeformed as it thermally contacts or expands due to heat generated fromthe light sources of the optical assembly 210. Therefore, lightuniformity of the backlight unit may be improved.

FIGS. 10 and 11 illustrate a backlight unit including light sourceassemblies according to a second embodiment. As shown in FIG. 10, an LCD500 according to this embodiment may include a bottom plate 510, anoptical assembly 540, an optical sheet 560, and a liquid crystal displaypanel 580. The bottom plate 510 may receive the optical assembly 540 andthe optical sheet 560 therein. The bottom plate 510 may also be a rearcover.

The optical assembly 540 received in the bottom plate 510 may include afirst layer 541, light sources 542, light guide plates 543, and areflective plate 544. The first layer 541 may be a board (or substrate)on which a plurality of light sources 542 may be mounted. An electrodepattern may be formed on the first layer 541 to connect an adapter thatmay supply power and the light sources 542. The first layer 541 may be aPCB formed of polyethylene terephthalate (PET), glass, polycarbonate(PC), silicon (Si), or other appropriate materials, on which theplurality of light sources 542 may be mounted. The first layer 541 maybe formed as a film.

The light sources 542 may be one of a light emitting diode (LED) chipand an LED package including at least one LED chip. In this embodiment,simply for ease of explanation, the light sources 542 will be describedas being an LED package. The LED package constituting the light sources542 may be classified into a top view type LED package and a side viewtype LED package depending on the direction of a light emission surface.The light sources 542 may be configured by using at least one of the topview type LED package in which a light emission surface may be formedtoward the upper side and the side view type LED package in which thelight emission surface may be formed toward the side.

The light guide plates 543 may be disposed in a direction in which lightmay be emitted from the light sources 542 and may serve to widely spreadlight formed incident from the light sources 542. In this embodiment,the light guide plate 543 may be configured such that a side contiguouswith the light source 542 may include a step that may allow aneighboring light guide plate 543 to be mounted thereon. A lower surfaceof the light guide plate 543 may be formed to slope, or positioned at anangle, to upwardly reflect light received from the light source 542. Thereflective plate 544 may be disposed on the lower surface of the lightguide plate 543 and may serve to upwardly reflect light which may bereflected downward from the light guide plate 543.

The optical assembly 540 including the first layer 541, the lightsources 542, the light guide plates 543, and the reflective plate 544may implement light in an edge manner. A plurality of light sourceassemblies 540 may be provided in the LCD 500. With reference to FIG.11, the foregoing light source assemblies 540 may be coupled in a recessformed on the cover member 510. The light source assemblies 540 may becoupled to the entire lower surface of the bottom plate 510. Thus,because the light source assemblies 540 that implement light in an edgemanner are formed on the entire lower surface of the bottom plate 510,they may function as a backlight unit that provides light in a directmanner.

As shown in FIG. 10, the optical sheet 560 may be positioned on theplurality of light source assemblies 540 formed on the lower surface ofthe bottom plate 510. The optical sheet 560 may be a diffusion sheetthat diffuses light or a prism sheet that concentrates light. Further, aplurality of optical sheets may be formed.

The optical sheet 560 may be mounted on the plurality of light sourceassemblies 540 and may be coupled to the fixing part 520 formed on theside wall of the bottom plate 510. Here, as shown in FIGS. 4A to 4Kaccording to the first embodiment, the optical sheet 560 may include aplurality of holes 565. Also, as shown in FIGS. 5A to 5C according tothe first embodiment as described above, the bottom plate 510 mayinclude a plurality of fixing parts 520.

Accordingly, as the holes 565 of the optical sheet 560 may be coupled tothe fixing parts 520 formed on the side wall of the bottom plate 510,the optical sheet 560 may be fixed to the bottom plate 510. Thus, theoptical sheet 560 may be prevented from being deformed as it contractsor expands due to heat generated from the light sources 542 of theoptical assembly 540. Therefore, light uniformity of the backlight unitmay be improved.

FIG. 12 illustrates a direct type backlight unit. Referring to FIG. 12,a backlight unit 600 may include a bottom plate 610, a reflective plate620, light sources 630, a diffusion plate 650, and an optical sheet 650.The reflective plate 620 may be positioned on the entire inner surfaceof the bottom plate 610 and may serve to reflect light emitted from thelight sources 630 upwards. The light sources 630 may be a CCFL (coldcathode fluorescent lamp), an HCFL (hot cathode fluorescent lamp), anEEFL (extended electrode fluorescent lamp), or other appropriate lightsource. A plurality of light sources may be positioned to be separatedat predescribed intervals. The diffusion plate 640 may serve to diffuselinear light emitted from the light sources 630 and may change it intosurface-type light. The optical sheet 650 may be positioned at an upperside of the diffusion plate 640.

The direct type backlight unit 600 as illustrated in FIG. 12 may use aplurality of lamps having a large diameter as light sources, and maycause increase in the thickness of the space within the bottom plate 610in which the light sources 630 are disposed. This may result in anincrease in the thickness of the backlight unit 600. Accordingly,because there may be a relatively large space between the light sources630 and the optical sheet 650, heat generated by the light sources 630may be prevented from being transferred to the optical sheet 650. Thus,the optical sheet 650 may be protected from being deformed by the heatby the light sources 630.

Meanwhile, the backlight units according to the first and secondembodiments may be configured to have the light source assembliesincluding very small LED light sources. For example, in the backlightunit according to the first embodiment as shown in FIG. 3, the secondlayer 230 may be positioned to cover the light sources 217, thediffusion plate 240 may be formed contiguously on the second layer 230,and the optical sheet 250 may be positioned on the diffusion plate 240.Further, in the backlight unit according to the second embodiment asshown in FIG. 10, the light sources 542 and the light guide plates 543may be formed, and then the optical sheet 560 may be disposed on thelight guide plates 543.

For example, the backlight units according to the first and secondembodiments may have a relatively thin structure as they may use verysmall LED light sources. Thus, the space between the LED light sourcesand the optical sheet may be very narrow. Heat discharged from the lightsources, therefore, may be directly transferred to the optical sheet. Inparticular, in case of the backlight unit according to the firstembodiment, there may not be sufficient space for releasing heat that isgenerated by the LED light sources. This may result in deformation ofthe optical sheet formed of a resin material as it contracts or expandsdue to the heat generated by the light sources.

Thus, in order to overcome this problem, in the first and secondembodiments, the plurality of holes may be formed on the optical sheetand coupled to the plurality of fixing parts that may be formed on thebottom plate. Accordingly, a margin, allowing for thermal expansion ofthe optical sheet due to heat generated by the light sources, may becreated between the holes and the fixing parts, thereby preventingpossible creases in the optical sheet. Also, as the optical sheetcontracts, the fixing parts may serve to apply tension to the opticalsheet to prevent the optical sheet from contracting. Thus, deformationof the optical sheet may be prevented.

FIG. 13 illustrates an LCD according to a third exemplary embodiment ofthe invention. As shown in FIG. 13, an LCD 700 according to the thirdembodiment may include a bottom plate 710, an optical assembly 740, anoptical sheet 760, and a liquid crystal display panel 780. The bottomplate 710 may receive the optical assembly 740 and the optical sheet 760therein. The bottom plate 710 may be a rear cover member.

The optical assembly 740 received in the bottom plate 710 may include afirst layer 741 and the light sources 742. The first layer 741 may be aboard (or substrate) on which a plurality of light sources 742 may bemounted. An electrode pattern may be formed on the first layer 741 inorder to connect an adapter that may supply power and the light sources542. The first layer 741 may be a PCB formed of polyethyleneterephthalate (PET), glass, polycarbonate (PC), silicon (Si), or otherappropriate materials on which the plurality of light sources 742 may bemounted. The first layer 741 may be formed as a film.

The light sources 742 may be one of a light emitting diode (LED) chipand an LED package including at least one LED chip. In this embodiment,simply for ease of explanation, the light sources 742 will be describedas being an LED package. The LED package constituting the light sources742 may be classified into a top view type LED package and a side viewtype LED package depending on the direction of a light emission surface.The light sources 742 according to this embodiment may be configured byusing at least one of the top view type LED package in which a lightemission surface may be formed toward the upper side and the side viewtype LED package in which the light emission surface may be formedtoward the lateral side.

A light guide plate 743 may be disposed in a direction in which lightmay be emitted from the light sources 742 and may serve to widely spreadlight formed incident from the light sources 742. A reflective plate 744may be disposed at a lower portion of the light guide plate 743 toreflect upwards light which may be reflected downward from the lightguide plate 743. The optical assembly 740 including the first layer 741and the light sources 742 may be positioned on the side of the bottomplate 710 as a backlight unit implementing light in an edge manner.

The optical sheet 760 may be positioned on the light guide plate 743.The optical sheet 760 may be a diffusion sheet that may diffuse light ora prism sheet that may concentrate light. A plurality of optical sheetsmay be formed. The optical sheet 760 may be mounted on the light guideplate 760 and may be coupled to the fixing part 720 formed on the sidewall of the bottom plate 710. Here, as shown in FIGS. 4A to 4K accordingto the first embodiment as described above, the optical sheet 760 mayinclude a plurality of holes 765. Also, as shown in FIGS. 5A to 5Caccording to the first embodiment as described above, the bottom plate710 may include a plurality of fixing parts 720. Accordingly, as theholes 765 of the optical sheet 760 may be coupled to the fixing parts720 formed on the side wall of the bottom plate 710, the optical sheet760 may be fixed to the bottom plate 710. Thus, deformation of theoptical sheet 760 may be prevented as it contracts or expands due toheat generated from the light sources 742 of the optical assembly 740.Accordingly, light uniformity of the backlight unit may be improved.

FIG. 14 illustrates an edge type backlight unit. Referring to FIG. 14, abacklight unit 800 may include a bottom plate 810, a reflective plate820, light sources 830, a light guide plate 840, and an optical sheet850. The reflective plate 820 may be positioned on an entire innersurface of the bottom plate 810 to serve to reflect upwards lightemitted from the light sources 830. The light sources 830 may be a CCFL(cold cathode fluorescent lamp), an HCFL (hot cathode fluorescent lamp),an EEFL (extended electrode fluorescent lamp), or other appropriatelight sources. The light sources 830 may be disposed at one side of thebottom plate 810.

The light guide plate 840 may be positioned on the side portion of thelight sources 830 and on the entire surface of the bottom plate 810. Thelight guide plate 840 may also serve to reflect light emitted from thelight sources 830 to change it into a surface-type light. The opticalsheet 850 may be positioned at an upper side of the light guide plate840.

The edge type backlight unit 800 illustrated in FIG. 14 may use aplurality of lamps as light sources having a large diameter increasingthe relative thickness of the space within the bottom plate 810 in whichthe light sources 830 are disposed. This may result in an increase inthe overall thickness of the backlight unit 800. Accordingly, becausethere may be relatively large space between the light sources 830 andthe optical sheet 850, heat generated by the light sources 830 may beprevented from being transferred to the optical sheet 850. The opticalsheet 850 may thus be protected from being deformed by the heatgenerated by the light sources 830.

Meanwhile, the backlight unit according to the third embodiment may beconfigured to have the light source assemblies including very small LEDlight sources. For example, the backlight unit according to the thirdexemplary embodiment of the invention may have a relatively thinstructure in which the very small LED light sources may be used. Thus,the space between the LED light sources and the optical sheet may bevery narrow. Accordingly, heat discharged from the light sources may bedirectly transferred to the optical sheet.

Also, in order to emit light with an equal luminance as that of thefluorescent lamp light sources, a large amount of current may berequired by the LED light sources. In this case, as the applied currentincreases the amount of heat generated by the LED may also increase.Then, the optical sheets that are formed of a resin material may bedeformed and may contract or expand due to heat emitted from the lightsources.

Thus, in the edge type backlight unit according to the third embodiment,a plurality of holes may be formed at the optical sheet and a pluralityof fixing parts may be formed at the bottom plate, wherein the holes ofthe optical sheet and the fixing parts of the bottom plate may becoupled to each other. Accordingly, a margin allowing for thermalexpansion of the optical sheet due to heat generated by the lightsources may be created between the holes and the fixing parts, therebypreventing possible creases in the optical sheet. Also, as the opticalsheet contracts, the fixing parts may serve to apply tension to theoptical sheet to prevent the optical sheet from contracting. Thus,deformation of the optical sheet may be prevented.

A display device is broadly described and embodied herein and mayinclude a display panel having a plurality of electrodes and pixels; abacklight provided adjacent to the display panel, the backlight unitincluding at least one light guide panel having at least one lightincident area to receive light from a first direction and a lightemitting area to emit light received through the light incident area ina second direction, the first and second directions being differentdirections; at least one light source, at least one incident area of thelight guide panel being adjacent to at least one light source to receivelight output; and a reflector adjacent to the light guide panel toreflect light towards the second direction; and at least one opticalsheet provided between the display panel and the backlight, the at leastone optical sheet including a first optical sheet; and a cover providedadjacent to the display panel or the backlight, wherein the coverincludes a first rail near a first side of the cover and a second railnear a second side of the cover, the first and second sides beingopposite sides, the first optical sheet has a first slot near a firstside and a second slot near a second side, the first and second sidesbeing opposite sides of the first optical sheet, and the first slot isfitted over the first rail and the second slot is fitted over the secondrail.

The display device is disclosed wherein the first slot is smaller thanthe second slot; wherein the first and second rails have the same size;wherein when the display device is positioned to be vertical such thatthe second direction is perpendicular to a direction of gravity, thefirst slot of the first optical sheet hangs onto the first rail, and thesecond slot is provided loosely over the second slot.

The display device is disclosed wherein the first optical sheet includesa plurality of tab portions, a first tab portion extending from thefirst side of the optical sheet and the first slot being provided on thefirst tab portion, and a second tab portion extending from the secondside of the optical sheet and the second slot being provided on thesecond tab portion; wherein the backlight is provided within a firstarea of the cover, and at least a portion of the first tab portion andthe second tab portion are provided outside of the first area; andwherein the at least one light guide panel is provided within a firstare of the cover, and the at least a portion of the first tab portionand the second tab portion are provided outside of the first area;wherein the at least one light guide panel is provided within a firstarea of the cover, and the at least a portion of the first tab portionand the second tab portion are provided outside of the first area.

Here, as shown in FIGS. 7 and 8G, display device is disclosed whereinthe cover 300 further includes a third rail near a third side 324, whichis between the first 321 and second sides 322, and the first opticalsheet 250 further includes a third slot near the third side 258, whichis between the first 255 and second sides 256 of the first opticalsheet, the third slot being fitted over the third rail, and the thirdslot being bigger than the first slot; and wherein the first opticalsheet includes a plurality of tab portions, a first tab portionextending from the first side of the optical sheet and the first slotbeing provided on the first tab portion, a second tab portion extendingfrom the second side of the optical sheet and the second slot beingprovided on the second tab portion, and a third tab portion 252extending from the third side 258 of the optical sheet 250 and the thirdslot 251 being provided on the third tab portion 252.

The display device is disclosed wherein the third rail 310 has a firstwidth l8 and a first length l7 and the third slot 251 has a first widthl10 and a first length l9, the first width l10 of the third slot beinglarger than the first width l8 of the third rail by 2 mm to 10 mm, andthe first length l9 of the third slot being larger than the first lengthl7 of the third rail by 0.15 mm to 1.3 mm; wherein the first rail has afirst width and a first length and the first slot has a first width anda first length, the first width of the first slot being larger than thefirst width of the first rail by 0.2 mm to 2 mm, and the first length ofthe first slot being larger than the first length of the first rail by0.15 mm to 1.3 mm; and wherein the second rail has a first width and afirst length and the second slot has a first width and a first length,the first width of the second slot being larger than the first width ofthe second rail by 2 mm to 10 mm, and the first length of the secondslot being larger than the first length of the second rail by 0.2 mm to2 mm.

A display device comprises a display panel having a plurality ofelectrodes and pixels; a backlight provided adjacent to the displaypanel; at least one optical sheet provided between the display panel andthe backlight, the at least one optical sheet including a first opticalsheet; and a cover provided adjacent to the display panel or thebacklight, wherein the cover includes a first rail near a first side ofthe cover and a second rail near a second side of the cover, the firstand second sides being opposite sides, the first optical sheet has afirst slot near a first side and a second slot near a second side, thefirst and second sides being opposite sides of the first optical sheet,the first slot is fitted over the first rail and the second slot isfitted over the second rail, and the first slot is smaller than thesecond slot.

The display device is disclosed wherein the first and second rails havethe same size; wherein the first optical sheet includes a plurality oftab portions, a first tab portion extending from the first side of theoptical sheet and the first slot being provided on the first tabportion, and a second tab portion extending from the second side of theoptical sheet and the second slot being provided on the second tabportion; wherein the backlight is provided within a first area of thecover, and at least a portion of the first tab portion and the secondtab portion are provided outside of the first area; and wherein the atleast one light guide panel is provided within a first area of thecover, and the at least a portion of the first tab portion and thesecond tab portion are provided outside of the first area.

The display device is disclosed wherein the first rail has a first widthand a first length and the first slot has a first width and a firstlength, the first width of the first slot being larger than the firstwidth of the first rail by 0.2 mm to 2 mm, and the first length of thefirst slot being larger than the first length of the first rail by 0.15mm to 1.3 mm; and wherein the second rail has a first width and a firstlength and the second slot has a first width and a first length, thefirst width of the second slot being larger than the first width of thesecond rail by 2 mm to 10 mm, and the first length of the second slotbeing larger than the first length of the second rail by 0.2 mm to 2 mm.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A display device comprising: a display panelhaving a plurality of electrodes and pixels; a backlight providedadjacent to the display panel, the backlight unit including at least onelight guide panel having at least one light incident area to receivelight from a first direction and a light emitting area to emit lightreceived through the light incident area in a second direction, thefirst and second directions being different directions; at least onelight source, at least one incident area of the light guide panel beingadjacent to at least one light source to receive light output; areflector adjacent to the light guide panel to reflect light towards thesecond direction; and at least one optical sheet provided between thedisplay panel and the backlight, the at least one optical sheetincluding a first optical sheet; and a cover provided adjacent to thedisplay panel or the backlight, wherein the cover includes a first railnear a first side of the cover and a second rail near a second side ofthe cover, the first and second sides being opposite sides, the firstoptical sheet has a first slot near a first side and a second slot neara second side, the first and second sides being opposite sides of thefirst optical sheet and facing each other, and the first slot is fittedover the first rail and the second slot is fitted over the second rail,wherein the cover further includes a third rail near a third side, whichis between the first and second sides, and the first optical sheetfurther includes a third slot near a third side, which is between thefirst and second sides of the first optical sheet and connected with anend of the first side and an end of the second side of the first opticalsheet, the third slot being fitted over the third rail, wherein thefirst side and the second side of the first optical sheet are is longerthan the third side of the first optical sheet and the second side ofthe first optical sheet is longer than the third side of the firstoptical sheet, and wherein the first slot is smaller than the secondslot and the third slot.
 2. The display device of claim 1, wherein thefirst and second rails have the same size.
 3. The display device ofclaim 1, wherein when the display device is positioned to be verticalsuch that the second direction is perpendicular to a direction ofgravity, the first slot of the first optical sheet hangs onto the firstrail, and the second slot is provided loosely over the second rail. 4.The display device of claim 1, wherein the first optical sheet includesa plurality of tab portions, a first tab portion extending from thefirst side of the optical sheet and the first slot being provided on thefirst tab portion, and a second tab portion extending from the secondside of the optical sheet and the second slot being provided on thesecond tab portion.
 5. The display device of claim 4, wherein thebacklight is provided within a first area of the cover, and at least aportion of the first tab portion and the second tab portion are providedoutside of the first area.
 6. The display device of claim 4, wherein theat least one light guide panel is provided within a first area of thecover, and the at least a portion of the first tab portion and thesecond tab portion are provided outside of the first area.
 7. Thedisplay device of claim 1, wherein the first optical sheet includes aplurality of tab portions, a first tab portion extending from the firstside of the optical sheet and the first slot being provided on the firsttab portion, a second tab portion extending from the second side of theoptical sheet and the second slot being provided on the second tabportion, and a third tab portion extending from the third side of theoptical sheet and the third slot being provided on the third tabportion.
 8. The display device of claim 1, wherein the third rail has afirst width and a first length and the third slot has a first width anda first length, the first width of the third slot being larger than thefirst width of the third rail by 2 mm to 10 mm, and the first length ofthe third slot being larger than the first length of the third rail by0.15 mm to 1.3 mm.
 9. The display device of claim 1, wherein the firstrail has a first width and a first length and the first slot has a firstwidth and a first length, the first width of the first slot being largerthan the first width of the first rail by 0.2 mm to 2 mm, and the firstlength of the first slot being larger than the first length of the firstrail by 0.15 mm to 1.3 mm.
 10. The display device of claim 1, whereinthe second rail has a first width and a first length and the second slothas a first width and a first length, the first width of the second slotbeing larger than the first width of the second rail by 2 mm to 10 mm,and the first length of the second slot being larger than the firstlength of the second rail by 0.2 mm to 2 mm.
 11. A display devicecomprising: a display panel having a plurality of electrodes and pixels;a backlight provided adjacent to the display panel; at least one opticalsheet provided between the display panel and the backlight, the at leastone optical sheet including a first optical sheet; and a cover providedadjacent to the display panel or the backlight, wherein the coverincludes a first rail near a first side of the cover and a second railnear a second side of the cover, the first and second sides beingopposite sides, the first optical sheet has a first slot near a firstside and a second slot near a second side, the first and second sidesbeing opposite sides of the first optical sheet and facing each other,and the first slot is fitted over the first rail and the second slot isfitted over the second rail, wherein the cover further includes a thirdrail near a third side, which is between the first and second sides, andthe first optical sheet further includes a third slot near a third side,which is between the first and second sides of the first optical sheetand connected with an end of the first side and an end of the secondside of the first optical sheet, the third slot being fitted over thethird rail, and wherein a length of the first slot in a directionparallel to the first side is less than a length of the second slot in adirection parallel to the second side and the length of the first slotin the direction parallel to the first side is less than a length of thethird slot in a direction parallel to the third side.
 12. The displaydevice of claim 11, wherein the first and second rails have the samesize.
 13. The display device of claim 11, wherein the first opticalsheet includes a plurality of tab portions, a first tab portionextending from the first side of the optical sheet and the first slotbeing provided on the first tab portion, and a second tab portionextending from the second side of the optical sheet and the second slotbeing provided on the second tab portion.
 14. The display device ofclaim 13, wherein the backlight is provided within a first area of thecover, and at least a portion of the first tab portion and the secondtab portion are provided outside of the first area.
 15. The displaydevice of claim 13, wherein the at least one light guide panel isprovided within a first area of the cover, and the at least a portion ofthe first tab portion and the second tab portion are provided outside ofthe first area.
 16. The display device of claim 11, wherein the firstrail has a first width and a first length and the first slot has a firstwidth and a first length, the first width of the first slot being largerthan the first width of the first rail by 0.2 mm to 2 mm, and the firstlength of the first slot being larger than the first length of the firstrail by 0.15 mm to 1.3 mm.
 17. The display device of claim 11, whereinthe second rail has a first width and a first length and the second slothas a first width and a first length, the first width of the second slotbeing larger than the first width of the second rail by 2 mm to 10 mm,and the first length of the second slot being larger than the firstlength of the second rail by 0.2 mm to 2 mm.
 18. The display device ofclaim 11, wherein the first side and the second side of the opticalsheet is longer than the third side of the optical sheet.